Abstract

In this paper, spin-dependent tunnel junctions fabricated by shadow mask (junction area ) and by lithography (junction area down to ) were studied. The junctions have NiFe and CoFe electrodes and the insulating barrier is formed by depositing a 10–30 Å thick Al layer, followed by a 1–3 min plasmaoxidation in an atmosphere. The -size junctions show tunnelingmagnetoresistances(TMR) of 10%–13.5% at room temperature (RT), with 50% decrease in TMR for a bias voltage of 220 mV. The junction resistances range from hundreds of Ω to tens of kΩ. The analysis of current distribution indicates that no geometrically enhanced magnetoresistance occurs in the cross-shaped -size junctions when the measured junction resistance is five times larger than the electroderesistance over junction area. The -size junctions show TMR of 17%–24% at RT, independent of the junction area, and have a resistance between 90 kΩ and 1 MΩ for the size (resistance-area products of ). The -size junctions show 50% decrease in TMR for a bias voltage of 430 mV, and high sensitivity